Apparatus for the manufacture of iron shot



March 13, 1951 R. R. HANCOX ETAL APPARATUS FOR THE MANUFACTURE 01-" IRONsno'rs 2 Sheets-Sheet 1 Filed July 23, 1948 FIG.

INVENTORS: ROBERT R. HANCOX GEORGE L. TUER. JR. J. STUTZMAN MILO BY aATTORNEYS.

March 13, 1951 R. R. HANCOX EIAL 2,544,678

APPARATUS FOR THE MANUFACTURE OF mom sno'rs Filed July 23-, 1948 2Sheets-Sheet 2 FIG 2.

INVENTORS: ROBERT R. HANCOX EORGE L. TUERJR MILO J. STUTZMAN Maw-Patented Mar. 13, 1951 APPARATUS FOR THE MANUFACTURE OF IRON sno'rRobert R. Hanco-x, Kansas City, Mo., George L.

Tuer, Jr., Cleveland Ohio, and Milo J. Stutzman, Kansas City, Mo.,assignors to Olin Industries, Inc., East Alton, 111., a corporation ofDelaware Application July 23, 1948, Serial No. 40,276

' 4 Claims. I

This invention relates to the manufacture of "shot and more particularlythe manufacture of iron shot useable as the projectile charge of shotshells, but also for other purposes, such as shot peening, cleaning ofcastings, and granite cutting.

Commercial shot aS used in shot gun shells or cartridges have heretoforeconsisted of lead or lead alloys in spite of various disadvantages towhich lead shot are subject. Such shot are usually manufactured bydropping the molten metal from the perforations in the bottom. of a panor riddle at top of a shot tower. During the fall through air, theglobules assume a spherical shape, solidify asshot having av diameterroughly dependent upon the size of the perforations. of the riddle, andare finally collected in a quenching medium such as water. Because of aunique combination of physical properties, lead can be fabricated into around shot of a desired size so efficiently and economically by themethod described that it has not proved commercially feasible tofabricate shot of other desirable, but more dimcultly workable, metalssuch as iron- In general, iron shot may be formed by one of two methods,namely, the method of. form, ing drops of molten metal and allowing themto fall into a quenching medium, and the method of. casting. For massproduction of the sizes of shot encountered in shot shells, thetechnique of casting is prohibitively expensive. Various dropformingmethods, including subdividing a falling stream of molten metal by meansof a heater member, atomizing, and the perforated crucible methodsimilar to that used in the making of. lead shot, have been usedheretofore in the attempted manufacture of iron pellets or shot. The

particles so produced consist of spheres, sphe-' roids discs,dumb-bells, and pear-shaped particles, or even irregular shapedparticles with little uniformity in size. In some instances, only ofshot formed by atomizing was found to be useable for ammunition. Inprior methods for making ferrous shot wherein an aperturedmember or droppan was utilized to subdivide the molten metal, it has been found thatthe apertures of said member very rapidly eroded or washed away so as toeffect a disadvantageous change in the size of the stream passed. Unlikethe practice of making lead shot, the size of orifices in a drop pancannot be depended upon to control the size of shot formed ofironbecause the iron wets the material surrounding the orifice.

A principal object of this invention, therefore,

2 is to provide an apparatus for producing ferrous shot.

Another object is to provide an improved apparatus for producing on alarge scale iron shot, a large proportion of which are of useable sizes.Another object is to provide an apparatus for producing iron shot ofgood spherical configuration. Other objects and advantages will beapparent from the following description and: accompanying drawing, inwhich:

Figure 1 is a schematic elevational view, partly in cross section, of apreferred embodiment of the invention;

Figure 2 is a schematic elevational view, partly in section, showing. amodified form of the apparatus of Figure 1;

Figure 3 is a plan view of the foraminous member used in the apparatus;and

Figure 4 is a fragmentary view, in section, of themember of: Figure 3.

In accordance with the present invention, iron shot having a favorableregularity of shape and ahigh uniformity of size; are. produced byinterposing, in the path of fall of. a stream of molten metal, a movingscreen whose active area is constituted of substantially more openspaces than of closed (solid) substance. Indeed it is preferable thatthe. openings in. the screen occupy at least 65% of the overall activearea of the screen. By active area is meant that portion of the screen.which, in normal operation, will be interposed: in. the path of fallingmolten metal. The molten metal may be dropped from a ladle, furnace, orcrucible, situated at an elevation above the screen.

After the stream of molten metal. passes through the screen, it issubdivided into particles which have the. desired volume. The particlesare then deposited in a quenching bath, through which, in the course offurther fall, they assume their final near-spherical shape and are set.The quenching. bath may be in the form of a spray or pool. of water orany other cooling liquid, with or without antioxidants, and should. bemaintained' at or slightly above room temperature. above F., thesphericity of the shot decreases about 5% for each 20 F. rise intemperature of the bath, but bath temperatures down to nearly freezingproduce satisfactory results.

The material of which the screen is made is preferably bibulous orbibulous-covered, although satisfactory results are attainable withnon-bibulous screens if a layer of water or other cooling liquid is.maintained on the screen at th region which traverses the path of thefalling molten metal. Consistent with the strength necessary towithstand the impact of the molten metal, without too much sacrifice ofopen area, textile fabric screens may be used. Bibulous screens formedof other fibers, such as ramie, synthetic textiles, asbestos, and thelike, may be used. Wire or plastic strands covered with bibulousmaterial supply means, such as a ladle (whichmay be a H small inductionfurnace) or a perforated crucible or pot, a continually cooledforaminous member of the type described herein for subdividing themolten metal'stream into molten shot, and a means for quenching andcollecting the shot. In the fall from the furnace, the molten metalstream will break up into globules, due to the influence of surfacetension. These globules are subdivided, upon meeting the screen fromwhich they emerge, into banana" shapes. Surface tension acts upon thetiny bananas to subdivide them into spheres and near-spheres before theyset.

The shot-making apparatus of Figure 1 includes means for dropping moltenmetal, such as the ladle having a lip 2. Disposed in a horizontal orinclined plane below the lip 2 is a rotatable foraminous member 3constructed of fabric or wire mesh having an open weave of a suitablemesh size. A suitable foraminous member 3 may be in the form illustratedin Figure 3 and consists of a circular-piece screen, the individualwires of which are covered with cotton. Alternatively, cotton mesh, orlacquered, enameled, or otherwise thermally insulated wire mesh may beused. The Screen 3 may be pierced by a hole t in order that the platemay be centrally mounted for rotation. Mounted upon the end of thevertical shaft 5 by any means, such as a combinationof washers and nut6, the screen is driven by a suitable means, such as electric motor' '3through shaft 5. A hoop 8 may be provided to hold the screen taut.Disposed below the screen 3 is a vessel i0 containing a quenching liquidH, such as water or any other suitable coolant, to a suitable depth forreceiving and solidifying the falling shot 12 formed at the screen. Inorder that the member 3 be continually cooled, the cotton covering ofthe screen is kept well wet with liquid at all times. To accomplishthis, a pip 13 terminating in nozzle 14 is so placed that portions ofthe cotton covered screen utilized for the subdivision of falling metalare alternately subjected first to the stream of cooling liquid issuingfrom nozzle l4, and then to the stream of molten metal, so that thescreen is wet when the metal strikes it. The water is vaporized as thehot metal strikes it, thus providing an insulating blanket of live steambetween the molten metal and the screen.

In the alternative form of apparatus shown in Figure 2, the screen 23,corresponding to the screen 3 of the previous embodiment, is situatedbelow the surface of the quenching medium in tank (0. Otherwise, theparts are identical with those previously described save that the watersupply pipe 13 and its nozzle M are omitted.

In the manufacture of iron shot for use in shot 4 gun shells, it isdesirable to produce as high a yield as possible within the size rangeof 0.055 to 0.157 inch in diameter. The present invention producesadvantageous yields of properly shaped shot within the size range justindicated. For example, utilizing the apparatus shown in Figure 2 withth screen one quarter of an inch under the surface of the quench bath,molten ingot iron poured at a temperature of 3100 F. through anatmosphere of air from an elevation of about 18 inches above the screen23, yielded 70% (of the input metal) within the size range indicatedabove and of good sphericity. In this operation the screen was acotton-covered wire screen having 10 mesh per lineal inch (mesh 0.077inch square, filament diameter 0.018 inch) and moving at a linealvelocity (at the mean. radius of impact) of 1.6 feet per second. Thevrate of pour was between and grams per:

second.

As another exemplary operation, utilizing the apparatus shown in Figure1 with a 'I-mesh cloth. screen, rotating on an axis inclined 26 awayfrom vertical, a yield of 80% within the size range aforesaid and ofgood sphericity was achieved. In this instance, the distance between,the crucible lip and the scrcen (point of impact) was 8 inches and therewas a distance of 30- inches between the screen and the surface of the.quench bath. The iron was poured at the rate. of 157 grams per secondand at a tempera-- ture of 3100 F. The screen was moving at a. velocityof 3.2 feet per second at the mean radius. of impact.

When, other things remaining the same as in the last example, thescreen-to-quench distance; was reduced to 6 inches and the rate of pourreduced to 144 grams per second, the yield was 80%, but the average sizeof the resultant shot increased. Experience indicates that, as thedistance between the screen and the surface of thequench bath isincreased (other variables re-- maining the same), the average size ofthe resultant shot decreases, but sphericlty improves..

With the screen less than about 6 inches abovethe surface of the quenchbath, the results are; less satisfactory from the standpoint of bothgood By reducing the inclination of the screen to- 15, providing a spaceof two feet between the-- screen and the quench bath, and maintaining.

other factors substantially the same as indicated in the paragraph nextabove, the yield was 81% with the average size of the shot reduced.

In addition to the yields indicated in the ex'-- amples given above,there are appreciable quantities of shot of good sphericity, but whosesize is outside the range of 0.055 to 0.157 inch. Such shot are suitablefor other purposes than use in shot shells.

For shot shell purposes, but not for some other purposes, it ispreferable to employ iron as pure as commercially feasible andrelatively free of carbon. To facilitate the shot formation from suchiron, it is preferable to elevate the tempera ture thereof to above 2800F. before pouring from the ladle. The rate of pour is so controlled asto keep the concentration of globules (below the screen) low enough thatthe likelihood of col lision between them (with resultant formation ofdumb-bells) is minimized.

In general, the greater the ratio of open area to obstructed area(filament) of the active portion of the screen, the higher the yield ofshot of good sphericity.

The depth of the liquid in tank [0 is thirty inches or more or, in anycase, sufficient to solidify the globules of metal before their fall isobstructed by the bottom or by other shot on the bottom.

In the embodiment of Figure 1, where the screen is situated above thesurface of the quenching bath, the cooling liquid must be fed at a ratesufficient to keep the bibulous screen soaked or saturated. Where abibulous screen is used, the velocity of movement is not of greatimportance-indeed the screen is moved only to assure that the incrementof screen, exposed to the molten iron at any instant, is cool and wet.

While the invention has been described with particular reference to themanufacture of iron shot for use as ammunition projectiles, it is to beunderstood that the apparatus may be used with other metals, and to makeshot for other purposes. Each different metal requires some adjustmentof the several variables and likewise the optimum sizing of the shot.

From the foregoing description those skilled in the art should readilyunderstand the invention and recognize that it accomplishes its ob-,iects. While several examples have been given for the purpose of ilustration, it is to be distinctly understood that the invention is notlimited to the details thereof.

Having thus described the invention, what is claimed and desired to besecured by Letters Patent is:

1. Ap aratus of the kind described comprising, in combination, supplymeans for maintaining a supply of molten metal and for discharging astream thereof. a screen arranged below said supply means and in thepath of a stream of molten metal falling from said supply means. saidscreen having substantially more than half its active area occupied byopen spaces, means for moving said screen transversely of the path ofthe stream of molten metal falling from said supply means, and a quenchtank arranged to receive particles falling from said scree 2. Apparatusof the kind described comprising, in combination, supply means formaintaining a supply of molten metal and for dis'charginga streamthereof, a screen arranged below said supply means and in the path of astream of molten metal falling from said supply means, means for movingsaid screen transversely of the path of the stream of molten metalfalling from said supply means, a quench tank arranged to receiveparticles falling from said screen, said screen having at leastsixty-five per cent of its area open, and said screen having at leastthe outer increments of its constituent strands composed of bibulousmaterial, and means for wetting said bibulous material with liquidcoolant.

3. Apparatus of the kind described comprising, in combination, supplymeans for maintaining a supply of molten metal and for discharging astream thereof, a screen arranged below said supply means and in thepath of a stream of molten metal falling from said supply means, meansfor rotating said screen in a direction transversely of the path of astream of molten metal falling from said supply means, and a quench tankarranged to receive particles falling from said screen, said screenhaving at least sixtyfive per cent of its area open.

4. Apparatus of the kind described comprising a screen composed ofstrands, said strands having at least their outer increments composed ofbibulous material, means for supplying a stream of molten metal to theupper surface of said screen, means for moving said screen transverselyof the path of a stream falling from said supply means, and means forcontinually wetting the bibulous material with liquid coolant,

ROBERT R. HANCOX. GEORGE L. 'I'UER, JR. IVIILO J. STUTZMAN.

REFERENCES CITED The following references are of record in the file ofthis patent:

